Question

How do I solve this ?

Answer 1

Look at the picture.

ΔZYX and ΔDYC are similar. Therefore the lengths of sides are in proportion:

$\dfrac{DC}{ZX}=\dfrac{DY}{ZY}$

DC = x

ZX = 16

DY = a

ZY = a + a = 2a

Substitute:

$\dfrac{x}{16}=\dfrac{a}{2a}$

$\dfrac{x}{16}=\dfrac{1}{2}$       multiply both sides by 16

$\boxed{x=8}$

Answer: CD = 8